Spark-plug



l. E.' GENN'.

SPARK PLUG. APPLICATION flu-:D AUG. 15. 191s.

Patented Jan. 13,1920.

UNITED sTATEs PATENT. OFFICE.

JoI'IN E. GENN, or CHICAGO, ILLINOIs'ASSIGNoR To STEWART-WARNER s'PEEDoMETER. CORPORATION, or cHIcAGo,'ILI.INoIs, A CORPORATION or VIRGINIA.

srAnmrLuG.

Application `filed August 15, 1918. Serial No. 249,939. I

To all whom t may concern:

Be it known that I, JOHN E. GENN, a citizen of the United States, and a resident of the city of Chicago, in the county of Cook and the State of Illinois, have invented certain new and useful Improvements in Spark-Plugs, of which the following is a Figure 1 1s an axial sectional view ofva I spark plug embodying this invention.`

. at line 2-2 on Fig. 1.

Fig. 2 is a detail section taken as indicated Fig. 3 is an elevation'of the "end portion of the plug showing the terminal Adifferently adjusted than in Fig. 1.

Fig. 1 shows the usual outer metallic shell,

1, in which the porcelain insulator,-2, vis se.

cured Iby a gland or bushing, 8, screwed'into the upper end of the shell, 1. The enlargement, 4, of the porcelain insulator is thus clamped between said bushing, 3, and'the internal shoulder, 5, of the shell, 1, with suitable packing washers of copper and asbestos interposed at the points of contact as indlcated at 6 and 7 .The central electrode, 8, is secured in the end of a conductor member, 9,

extending axially through the porcelain the.

portion of the bore in the porcelain which accommodates such conductor, 9, belng longitudinally corrugated as seen in Fig. 2, and

the conductor itself being threaded through a considerable portin of its length from the upper end downward; the diameter of this threaded portion is such that it will be practically centered between the ribs, 10, ofthe corru ated Wall of the bore in the porcelainy with ]ust suflicient clearance for rapid assembly, and slight clearance 1s also provided in the reduced portion of the bore surrounding the electrode, 8. 'A metallic cap, 11, formed with a threaded hub, 12, engaging the threaded electrode, 9, and with a iiange, 13, whose edge, 14, is crimped or- Speeication-of Letters Patent-. Patented Jan. 13, 1920.

rolled into a groove, 15, formed in the porcelain near upper end, serves to longitudinally posltlon the conductor, 9, with its 'lower end abutting the shoulder, 16, inthe porcelain, and lby' thus vassembling the parts with a'iilling of wet cement, 17, occupylng all the space 'ubetween the conductor, 9, and the electrode, 8, and the walls of the porcelain insulator, 2, the cement as it intervening grooves, 18, are integrally conthe cement occupying the groovesnected b liread'onl the conductor,'9, so that of the t the body of cement in the corrugated b ore of the porcelain 'constitutes one continuous mass' which is firmly locked against rotatlon 'by the corrugation of the bore and whlch adheres strongly vto the conductor, 9,

largely by reason' of `lts threads which are'.

particularly well adapted to provide a good bond wlth the cer-nent if they areformed by pressing or rolling, instead of being cut and smoothly finished .in lthe surface'of the.. finetal. It maybe noted that the corrugatlons formed by the ribs, 10, are discontinued at 19, and from this point to the'end of the porcelain the; bore is c lindrical to accommodate the-hub, 12, of t e cap, 11.-

The rounded electrode, 20, which is fixed in the ower endf'of the shell, 1,`may be a,

wire of the same material as the electrode, 8,:

and is bent hook shaped. It is preferably jacent a part of :the electrode 8, which is is of relatively low intensity, the spark may be confined to the most closely adjacent parts of the electrodes, 8 and 20, 'um mg trom the point, 21, of the hook to t e e ectrode, 8, it will not be confined to a air of points when the intensity of the electrlcal energy becomes sucient to produce a heavier spark; but, in the latter case, the arc may spread out into a fan shape, the discharge being distributed along the length of the electrode, 20, from its point, 21, ack to the bend of its hook form and along the corresponding length of the electrode, 8, out to its tip, 22. With a Apositioned with the point, 21, of the hook adconstantly heavy discharge, this arrangement will result in 4a much greater length of life for the electrode than is possible where the discharge is practically lforced' to occur entirely between the points or ends of the wires. y

The projecting portion of the threaded conductor, 9, is fitted with a binding nut, 23, formed with a conical end portion, 24, and with grooves, 25 and 26, for the reception of certain forms of terminal eli s, not shown, but commonly applied to con uctor wires-0f Athe ignition circuit. Certain other forms of terminals such as fiat, annularor slotted members, or even the bare ends ofthe wire itself, may be simpl' clamped between the metallic cap, 11, of t ie spark plug, and the flange, 27, of the binding nut when the latter is applied in the position shown in Fig. 3. To adapt the plug for connection to a still larger variety of terminals, there is provided a hollow ball, 28, which may be clamped in position as shown in Fig. 1 between the flange, 29, of the binding nut and the top surface of' the cap,'11, thus providing a. spherical surface which may be engaged by certain terminals designed for the purpose and usuall consisting of apair of substantially parallel spring members having opposed a ertures or iiidentations of somewhat sma-l er diameter than the ball, 28, and adapted to be seated thereon.

I claim:

1. In a spark plug, an insulating member having a longitudinally corrugated bore, a conductor disposed therein and secured by cement filling the space between the surface of such conductor and the corrugated Wall of the insulator.

2. In a spark plug, an insulating member having a longitudinally corrugated bore a conductor disposed therein and formed'with surface corrugations running transversely of its axis, and cementfilling the spae'between the corrugated surfaces of theI conductor and the insulatin bore.

3. In a spark p ug, an insulating member having a. longitudinally corrugated bore, a conductorl disposed therein having a corrugated surface formed by a screw thread thereon, and cement filling the space between the threaded surface of the conductor ggd the corrugated surface ofthe insulator 4. In a spark plug, an insulating member, a metallic top for the insulator including a hubportion internally threaded an'd externally corrugated, the insulator having a bore in which said hub is loosely accommodated, a conductor for the insulated electrode of .fthe spark plug comprising a threaded por- "ition lengaged with said .hub ofthe cap and extending into the bore of the insulator, and cement filling the spaceinthelbore around 4such threaded conductor and said hub of the cap.-

5. In a spark p1ugin vcombination with the insulated electrode, a terminal for the same comprising a threaded conductor, a binding nutA thereon and an approximately spherical member removably held on said conductor by said binding nut. y

6. In a spark plug, an insulfator provided with a metallic cap at its outer end, an velectrode carried by said insulatorl and a terminal for the electrode comprising a threaded conductor, a binding nut comprising a ange, and a longitudinally extended portion of smaller diameter, and an approximately spherical shell apertured to receive -said1 smaller portion of said ifut, to be held upon the conductor between the flange of said nut and the insulator cap.

In testimony whereof I have hereunto set my hand at Chicago, Illinois, this 12th day of August, 1918.

J. E. GENN. 

